If the guru makes himself or herself unavailable for association, how can one make an informed determination about their qualifications?  One has to go by popular opinion, which is the most hopeless basis for such a decision.  It is better not to accept such a person as a guru.

A personal relationship between the guru & disciple must be established prior to accepting each other.  There may surely be exceptions to this.  However, we must distinguish between exceptions and the general rule.  Imitating an advanced guru, like Srila Prabhupada, who has the empowerment of being the exception, is dangerous; following his instructions and the general rule in this matter is safe. 

Thus, in anga, (arm), number 13 of the science of bhakti states,

“One should not accept an unlimited number of disciples”.

In Easy Journey to Other Planets, EJ 1, Anti-Material Worlds, Srila Prabhupada wrote:

“The following details outline a general practice by which one can prepare himself for an easy journey to the Vaikuntha, (antimaterial) planets, where life is free from birth, old age, disease and death. General practice, angas of bhakti, (positive functions): …

1. 13. He must not take on unlimited disciples.

This means that a candidate who has successfully followed the first twelve items can also become a spiritual master himself, just as a student becomes a monitor in class with a limited number of disciples.…”

In The Science of Self-Realization, Srila Prabhupada wrote:

“The sastras enjoin that before we take a guru, we study him carefully to find out whether we can surrender to him.

We should not accept a guru suddenly out of fanaticism. That is very dangerous.

The guru should also study the person who wants to become a disciple to see if he is fit.

That is the way a relationship is established between the guru and disciple.”